1. Field of the Invention
The present invention relates to apparatus for regulating the deployment characteristics of an airbag cushion. More specifically, the present invention relates to apparatus and methods of their use for temporarily restraining the longitudinal expansion of a deploying airbag cushion to allow the cushion to achieve its fullest transverse width prior to expanding toward a vehicle occupant such as an out-of-position occupant.
2. Description of Related Art
Safety belts are designed to protect the occupants of a vehicle during events such as automobile collisions. In low-speed collisions, the occupants are generally protected from impact with objects located inside the vehicle such as the windshield, the instrument panel, a door, the side windows, or the steering wheel by the action of the safety belt. In more severe collisions, however, even belted occupants may experience an impact with the car's interior. Airbag systems were developed to supplement conventional safety belts by deploying into the space between an occupant and an interior object or surface in the vehicle during a collision event. The airbag acts to decelerate the occupant, thus reducing the chances of injury to the occupant caused by contact with the vehicle's interior.
Many typical airbag systems consist of several individual components joined to form an operational airbag module. Such components generally include an airbag cushion, an airbag inflator, a sensor, and an electronic control unit. Airbag cushions are typically made of a thin, durable fabric that is folded to fit into a compartment of a steering wheel, dashboard, interior compartment, roof, roof rail, roof compartment, or other space in a vehicle. The airbag inflator is in fluid communication with the airbag cushion, and is configured to produce a gas to inflate the cushion when it is needed. The sensors detect sudden decelerations of the vehicle that are characteristic of an impact. The readings taken by the sensors are processed in the electronic control unit using an algorithm to determine whether a collision has occurred.
Upon detection of an impact of sufficient severity, the control unit sends an electrical signal to the inflator. The inflator uses one of many technologies currently known in the art to produce a volume of an inflation gas. The inflation gas is channeled into the airbag, inflating it. Inflation of the airbag causes it to deploy, placing it in a position to receive the impact of a vehicle occupant. After contact of the occupant with the airbag and the corresponding deceleration of the occupant, the airbag rapidly deflates. To accomplish this, the inflation gas is vented from openings in the airbag, deflating it and freeing the occupant to exit the vehicle.
As experience in the manufacture and use of airbags has increased, the engineering challenges involved in their design, construction, and use have become better understood. Most airbag systems are designed to rapidly inflate and provide a cushion in proximity to a vehicle occupant. Many such cushions are configured to be placed in front of a vehicle occupant. Placement of the cushions is determined based on presumptions made of the position occupied by a vehicle occupant in a vehicle during normal operation of the vehicle. Thus, a vehicle occupant enjoys optimal protection from a specific airbag when the occupant is in the presumed range of positions when the airbag deploys.
In some situations, injuries have been noted to occur when a vehicle occupant is “out of position” with regard to the presumed position discussed above. Some such injuries have been attributed to incidents in which vehicle occupants located out-of-position during the deployment of an airbag cushion are located in the path of the inflating cushion. Currently available airbag systems rapidly inflate a cushion in front of an occupant during a collision. This inflation process is generally difficult to regulate, however, and some regions of the cushion may inflate before others, increasing the risk of injury to out-of-position occupants located near these early-filling portions of the cushion.
Potential injury to out-of-position occupants could be reduced and/or avoided by the use of systems capable of causing full radial expansion of an airbag cushion prior to placement of the cushion in front of the vehicle occupant. Similarly, injury could be reduced by the use of systems capable of reducing the forward momentum with which an airbag cushion is directed toward a vehicle occupant. Some systems currently available to regulate cushion expansion and deployment often utilize passive tether systems such as “break-tethers”—tethers configured to first hold an airbag cushion at a specified state and then to rupture at a specified load to release the cushion and allow full cushion deployment. Although useful, such systems have proven complex, with a large number of variables present in configuring a break tether for a specific application, and a large number of variables which may affect the performance of the tethers. Other technologies utilize active tether systems which have several characteristics which may be actively controlled by systems of the vehicle. These technologies are also very complex and more expensive to implement and use in a vehicle.
Accordingly, a need exists for airbag deployment restraint devices for use in vehicles to regulate the deployment characteristics of an airbag cushion such that out-of-position vehicle occupants receive a more even load during inflation of the airbag cushion. It would be specifically beneficial to provide an airbag deployment restraint device capable of forcing the deploying airbag cushion to assume its fullest radial width prior to fully expanding toward a vehicle occupant, thus presenting a broad surface area for potential contact with the vehicle occupant. There is a similar need for devices capable of regulating the momentum with which an airbag cushion expands toward a vehicle occupant. It would be a further advantage in the art to provide such an airbag deployment restraint device that is compatible with existing airbag cushion and housing designs to avoid the costs associated with the customization of existing airbag modules. Such airbag cushion deployment restraint devices and methods for their use are provided herein.